To avoid structural damage from excessive external force, the torque wrench is typically designed with overload protective measures. So, in case where the applied force of the pressure handle exceeds the preset value, the sheath end and pressure handle will move alternatively, thus preventing structural damage arising from continuous application of force by the user. With regard to a conventional structure of overload protective measure, a ratchet ring is typically mounted within the groove at the sheath end of torque wrench. The interior of the ratchet ring is provided with a supporting surface for articulation during positive and reverse rotation of sheath end, whereas the exterior of the ratchet ring is normally positioned securely by a flexible bead. In case the applied force of the pressure handle of torque wrench exceeds the preset value, the sheath end will activate the ratchet outside the ratchet ring to forcibly cross over the flexible bead, thus the sheath end and pressure handle will move alternatively to prevent structural damage. However, it has been found from practical experience that, owing to the sharp ratchet of ratchet ring, a bigger frictional wear will likely occur between the ratchet and groove of torque wrench during the former one crossing the flexible bead. In such case, the ratchet of ratchet ring will be broken and deformed rapidly, thus reducing the intended function of overload protection at the handle end and greatly shortening the service life of torque wrench. Also, it is unlikely to preset accurately the torque due to the strong friction of movement, leading to an unstable state against ideal utility model. Additionally, there is available with another typical structure for overload protection that is mounted onto the middle section of the pressure handle of the torque wrench. The principle of operation is that overload protection can be achieved through alternative movement of two components. However, if the end users continue to apply force during the movement, the component at one side will further bump the structural body of the pressure handle, leading to consequent damage.
Therefore, with a view to the above-mentioned disadvantages of typical torque wrench, this industry shall assume the responsibility to make some pioneering R& D and innovations for an ideal utility model.